1. Field of the Invention
The present invention generally relates to a method of providing multicast services, and particularly relates to a method of providing multicast services by having an information delivery apparatus deliver multicast information to wireless terminals residing in a service area through wireless routes. The present invention further relates to an information delivery apparatus and a wireless terminal used in such a method of providing multicast services.
2. Description of the Related Art
In recent years, applications that deliver music and video contents through the Internet have been attracting much attention. Use of wireless communication as an access link has an advantage in that information delivery services can be easily provided to users. If music or video contents are delivered as part of such services through a network that includes wireless routes as an access link, resulting merits are enormous.
In a general configuration of multicast service delivery systems that deliver multicast information such as music and video contents through wireless routes, a wireless base station (i.e., information delivery apparatus) transmits multicast information to a plurality of wireless terminals, and these wireless terminals simultaneously receive the multicast information. If the system is configured such that one-to-one communication is carried out between the wireless base station and each of the wireless terminals, the same information having the same contents needs to be delivered through separate channels to individual wireless terminals that are requesting the service. Such a configuration cannot make efficient use of communication resources.
The same multicast information is thus transmitted at once to a plurality of wireless terminals as part of the delivery service. In such a case, each wireless terminal experiences different quality of reception when receiving the multicast information if the wireless terminals are situated in different wireless communication environments. As shown in FIG. 17, for example, wireless terminals H and J that are relatively closer to the wireless base station BS are situated in relatively better communication environments, so that quality of reception is relatively high when receiving multicast information from the wireless base station BS. Since wireless terminals F, G, and I that are situated farther away from the wireless base station BS than the wireless terminals H and J experience relatively poor communication conditions, quality of reception would be poorer. Further, wireless terminals A, B, C, D, and E that are positioned close to a service area Es far away from the wireless base station BS suffer much worse communication environment, so that quality of reception of receiving multicast information from the wireless base station BS would be much poorer.
When multicast services are rendered by using one-to-n wireless communication between the information delivery apparatus and each wireless terminal as described above, each wireless terminal receiving the multicast services may differ in its reception quality. If reception quality varies, there may be a situation in which too many errors are made during reception so as to fail to meet required reception quality.
Accordingly, there is a need for a method of rendering multicast services that can deliver multicast information to wireless terminals experiencing different reception conditions in such a manner as to achieve sufficient reception quality at each of the wireless terminal.
Further, there is a need for an information delivery apparatus that is suitable for such a method of rendering multicast services.
Moreover, there is a need for a wireless terminal that is suitable for the method of rendering multicast services.